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 NEW  Matt presents bias and operation data for the 6V6 tube in SE operation - 6V6 Single-Ended (SE) Ultra Linear (UL) Bias Optimization.

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 Post subject: Re: 6CY7 Stereo Amp
PostPosted: 29 Oct 2015, 04:43 
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Joined: 26 Sep 2015, 13:59
Posts: 56
Thanks for these responses, very helpful. As one born in the 60s and discovering HiFi through 70s and 80s valves were generally considered 'old hat'. My first amps were a pair of Mullard 5/10s made by my dad - I could'nt wait to get rid of them at the time to get some 'modern' transistor amps. Now I'd give anything to have them back!

There is no denying that my 25w Audio Innovations valve amp is every bit as 'loud' as my Quad 405 - way louder than any sane person could use. But 1.3w does sound very low. Would I need particularly efficient speakers for it? I was thinking of building a pair of LS35s which are, I think, around 89db. Shoud I go for a pair of Fostek single driver units instead?

Thanks again for all your advice.

Mark


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 Post subject: Re: 6CY7 Stereo Amp
PostPosted: 29 Oct 2015, 16:03 
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Joined: 06 Apr 2009, 10:08
Posts: 1393
Location: US Pacific Northwest
RevM wrote:
But 1.3w does sound very low. Would I need particularly efficient speakers for it?
Mark;

All I can tell you is this: As I sit here typing, I am listening to this amp connected to a set of ≈89dB speakers here in my 10' x 12' office. The volume control is set to about the 11:00 position and the music is at a very comfortable listening level. The "Young Dubliners" song currently playing (Foggy Dew) is loud, clear, and energetic. I just turned the amp up to full volume and it was uncomfortable to which to listen at that level.

Nope, this amp will never make your neighbors call the police. But if you want a very clear sounding and musical amp which you can listen to every day and enjoy, this is a great build. IMHO.

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 Post subject: Re: 6CY7 Stereo Amp
PostPosted: 29 Oct 2015, 20:29 
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Joined: 08 Aug 2009, 03:11
Posts: 2159
Location: Chilliwack, BC
My Baby Amp is 2.5W/channel from 6FD7's and I listen to them on 85dB bookshelves. I can't turn them past 1-o'clock on the volume as multimedia speeks on my computer here and stay sane.
(mind you, I listen to Jazz, not Metal ;) )

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* Ratings are for transistors - tubes have guidelines*
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 Post subject: Re: 6CY7 Stereo Amp
PostPosted: 30 Oct 2015, 13:43 
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Joined: 06 Jun 2008, 18:23
Posts: 4833
Location: Australia
Matt, you may have seen I built some speakers around the 98db efficient 12" Beyma concentrics. Because of thier extremely low Qts they only need about 33ltrs of box to produce bass down to about 50hz (tested with ear and test CD). My 5.8W 300B, The Silver Draggon, can produce deafening levels of undistorted music. In fact I have never been able to turn it up to 11, 5 to 6 just gets too painfull.

For a week or two, recently, I powered the speakers with my (your Lace Wood) 6V6 amp, Black Lace. Once more this low power, sweet sounding amp played at high volume levels through the Beymas (VoXConcentriC). I used my stereo subbies to bring up the bottom end.

I have just ordered the 15" version of the Beyma concentrics. Slightly more efficiency at 99db but a better fs at 33hz and a better Qts at 0.29. What I'm am hoping for, in 120ltr box, is a deeper bass. I'm hoping these new speakers will work without subbies. If not no big deal.

The beauty of high efficiency speakers is they will work with any amp, are extremely detailed and dynamic and (depending on the drivers used) can work in smaller boxes. My 330mW UX-171A amp plays well through my current Beymas. The Beyams are not for every one but voices and brass are stunning and over the last three or four months of constant listening (4 hours a day, 5 days a week), I have really fallen in love with them.

If you like your uPower amps, something like the Beymas, will help appreciate them in a whole new light. They have shown me just how good my Silver Dragon really is.

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Projects: "Sanctum" - 12AU7 and 6AS7 direct coupled headphone amp | "retro-Oatley 6J6" - 6J6 push-pull headphone amp with OPTs | "Mimic Carbon" - carbon resistors and PIO caps. MM phono preamp
Website: retro-thermionic


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 Post subject: Re: 6CY7 Stereo Amp
PostPosted: 31 Oct 2015, 04:08 
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Joined: 26 Sep 2015, 13:59
Posts: 56
Thanks guys for all your help. I am very excited about (re)discovering the joy of valves and the beauty and purity of their sound. It is refreshing to find a forum like this one where i can ask stupid questions and not get flamed!

What I need now is to find a source of affordabe transformers and chokes in the UK. They are so expensive!


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 Post subject: Re: 6CY7 Stereo Amp
PostPosted: 31 Oct 2015, 05:08 
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Joined: 08 Aug 2009, 03:11
Posts: 2159
Location: Chilliwack, BC
You're very welcome! :D

I always say, "There are no stupid questions, but by golly, I sure have heard a LOT of stupid answers!" ;)

And I hear ya on chokes... even in Canada, an iron order can get TRIPLED with shipping/customs from the states :eek:

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* Ratings are for transistors - tubes have guidelines*
Home: GeeK ZonE
Work: Classic Valve Design


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 Post subject: Re: 6CY7 Stereo Amp
PostPosted: 31 Oct 2015, 05:52 
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Joined: 02 Mar 2009, 12:41
Posts: 1031
Location: Vänersborg, Sweden
RevM wrote:
What I need now is to find a source of affordabe transformers and chokes in the UK. They are so expensive!


Have you ever checked this guy: Mike's Living In The Past It may seem that what he sells (Danbury made) are a bit "amateurish", but I have used his transformers (big and small) and I am VERY satisfied with the quality and the price.

Try him out and we may perhaps discuss another but more intriguing project .... (let you know later).

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 Post subject: Re: 6CY7 Stereo Amp
PostPosted: 21 Nov 2015, 11:14 
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Joined: 19 Oct 2013, 12:44
Posts: 6
Location: Northern Michigan
I wonder what a push pull amp would sound like with these tubes?
Or are these tubes like the 6EM7 & 6FD7, only sound good in SE applications?


Rgds,
Yo


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 Post subject: Re: 6CY7 Stereo Amp
PostPosted: 21 Nov 2015, 11:54 
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Joined: 06 Apr 2009, 10:08
Posts: 1393
Location: US Pacific Northwest
yoaudio wrote:
I wonder what a push pull amp would sound like with these tubes?
Or are these tubes like the 6EM7 & 6FD7, only sound good in SE applications?
This is really a two part issue. The first is issue is stage matching and topology. Because you are starting with two dissimilar triodes in one envelope, matching becomes a larger issue because well matched power stages may result in unmatched signal stages. So whatever design you develop needs to include provisions for manual output stage balance. Then comes the topological matter of what to do with the signal triodes. If you build a LTP then the matching issue rises it's head again. You could use one signal triode as a concertina to drive the PP stage and then use the other signal triode as the drive amplifier. In any event, the design becomes complex. One of the beauties of these tubes in the SE driver and power stage configuration is simplicity of design. One tube per channel with just a few components.

The second issue concerns for what you're looking in the PP design. If it's more power then you're using the wrong tube. In pure class A PP you could significantly reduce the 2nd harmonic response, but that's what gives the tubes their unique sound in the first place. I guess I personally don't see the point of going through all the complexities of making these work in a PP configuration when there are so much better options.

Personally, for anyone looking for an inexpensive PP triode amp, I would suggest a 6AS7 PP output stage run in class A. A well balanced LTP driver will drive this configuration and give you a very sweet sounding topology.

That's just my thought on the matter. YMMV. :D

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It's all about the Glass!
http://www.CascadeTubes.com
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 Post subject: Re: 6CY7 Stereo Amp
PostPosted: 21 Nov 2015, 17:54 
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Joined: 06 Jun 2008, 18:23
Posts: 4833
Location: Australia
The beauty of 6AS7s is two power triodes on the one bottle. I have a real soft spot for these tubes having built a simple SE amp with this tube and 12AX7 and a headphone amp with the same tubes. Both really very good amps. Getting away from two triodes in one bottle an EL34 PP amp in UL mode would produce around 40W and have all those lovely EL34 harmonic characteristics.

Both tube are cheap and lots of NOS NIBs around two for just a few dollars.

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Projects: "Sanctum" - 12AU7 and 6AS7 direct coupled headphone amp | "retro-Oatley 6J6" - 6J6 push-pull headphone amp with OPTs | "Mimic Carbon" - carbon resistors and PIO caps. MM phono preamp
Website: retro-thermionic


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